Analysis of the high seed storability trait in indica rice "Fuxiangzhan"

As the duration of rice seed storage increases, the storability of the rice deteriorates, with the seed losing its vigor, especially under conditions of high temperature and high humidity, as occurs in the summer in southern China. The maintenance of rice seed longevity ("shelf life") during storage is central not only to national food security but also to the conservation of germplasm resources and the security of the seed industry. In the current study, the characteristics of the impacts of artificially accelerated aging stress on seed vigor in two indica rice cultivars, namely the high-storability "Fuxiangzhan" and low-storability "Hang2", were compared. Between 14 and 21 days of artificial aging, the seed vigor of "Hang2" decreased rapidly and the starch grain structure, observed by scanning electron microscopy, showed serious damage, whereas seeds of "Fuxiangzhan" still exhibited strong seed vigor and good starch grain structure after 21 days of artificial aging. Quantitative analysis of the seed embryo proteome showed that the biosynthesis and metabolism of lipids, proteins and carbohydrates, genetic information processing, transcriptional regulation, nutrient retention, signal transduction and redox regulation showed marked differences between "Fuxiangzhan" and "Hang2" at various time points during artificial aging. Differentially expressed proteins between Fuxiangzhan and Hang2 were significantly enriched in four metabolic pathways: linoleic acid metabolism; cutin, suberin and wax biosynthesis; glutathione metabolism; and glycerophospholipid metabolism. We speculate that the possible reasons for the longer shelf life of "Fuxiangzhan" seeds were that the lipid oxidase activity and the linoleic acid peroxidation rate of the seed embryos were lower than in "Hang2", and that the seeds had an improved protective barrier associated with greater concentrations of cutin and other waxes. Under high temperature and humidity stresses, the glutathione antioxidant system played a role in rapidly scavenging reactive oxygen species and achieving signal transduction in "Fuxiangzhan" seed embryos, where membrane integrity was maintained by the synthesis of higher glycerophospholipid concentrations in this high-storability cultivar. This study lays a firm foundation for the characterization of rice seed storability, which could be exploited in the breeding of rice cultivars with greater storability ("longer shelf life") under stress conditions.